RESUMEN
INTRODUCTION: Optic neuritis (ON) in neuromyelitis optica spectrum disorders (NMOSD) may occur at the onset of the disease, during relapse attacks, or both. It is well known that ON in NMOSD may cause permanent visual disability, but the influence of the time of its occurrence has not been investigated. OBJECTIVE: We evaluated the effect of the time of ON occurrence on visual outcome in a cohort of NMOSD patients. METHODS: We retrospectively analyzed the medical records of NMOSD patients with ON who met the 2015 International consensus criteria for NMOSD diagnosis. We assessed demographic and clinical data, the Expanded Disability Status Scale (EDSS), and visual disability according to the scores of the Kurtzke Visual Function Scale (KVS) and Wingerchuk's Optic Nerve Impairment Scale (WONIS). We divided patients into three groups according to the time of ON occurrence: (1) ON at disease onset; (2) ON exclusively in relapse attacks; and (3) ON at both disease onset and in relapse attacks. RESULTS: Out of 187 patients with suspected NMOSD, 85 (42.4%) met the inclusion criteria. ON occurred exclusively at the disease onset in 16 (18.8%) patients, exclusively in relapse attacks in 43 (50.6%) patients, and at both the onset and in relapse attacks in 26 (30.6%) patients. There was no significant difference in the EDSS scores of the groups. In comparison with patients with ON exclusively occurring during relapse attacks, patients with ON at disease onset had higher KVS scores (p = 0.009) and WONIS scores (p = 0.005). Patients with ON at both onset and in relapses had a larger number of ON attacks and NMOSD relapses, as well as the poorest visual outcome. CONCLUSIONS: ON at disease onset is a predictive factor for poor visual outcome in NMOSD patients.